1. Field of the Disclosure
The present invention relates generally to imaging, and more specifically, the present invention is directed to high dynamic range image sensors having gapless microlenses.
2. Background
Image sensors have become ubiquitous. They are widely used in digital still cameras, cellular phones, security cameras, as well as, medical, automobile, and other applications. The technology used to manufacture image sensors, such as for example complementary metal-oxide-semiconductor (CMOS) image sensors (CIS), has continued to advance at a great pace. For example, the demands for higher resolution and lower power consumption have encouraged the further miniaturization and integration of these image sensors.
High dynamic range (HDR) image sensors have become useful for many applications. In general, ordinary image sensors, including for example charge coupled device (CCD) and CMOS image sensors, have a dynamic range of approximately 70 dB dynamic range. In comparison, the human eye has a dynamic range of up to approximately 100 dB. There are a variety of situation in which an image sensor having an increased dynamic range is beneficial. For example, image sensors having a dynamic range of more than 100 dB dynamic range are needed in the automotive industry in order to handle different driving conditions, such as driving from a dark tunnel into bright sunlight. Indeed, many applications may require image sensors with at least 90 dB of dynamic range or more to accommodate a wide range of lighting situations, varying from low light conditions to bright light conditions.
One of the challenges with providing miniaturized higher resolution image sensors is that the gap distances between the microlenses in known image sensors limit the density of the microlenses in the image sensor. Indeed, as the gaps between lenses become smaller, there is an increased risk of neighboring microlenses merging together during the reflow process, which reduces yields. As a consequence, maintaining minimum gap distances between microlenses have resulted in reduced fill factors and lower quantum efficiencies in known images sensors.
Corresponding reference characters indicate corresponding components throughout the several views of the drawings. Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention.